In conventional methods of decorating a key top of a push button switch with metallic luster or pearl luster tone, the following methods are known, for example, a method of molding by mixing metallic powder or pearl pigments in resin or rubber ingredients, a method of painting or screen-process-printing paints containing metallic powder or pearl pigments, a method of preparing a metallic film of aluminum chrome, or the like. on the surface of the key-top by vacuum evaporation method or sputtering method, and a method of metal plating.
However, the method of molding by mixing metallic powder or pearl pigment with resin and rubber causes a lack of uniformity in a stripped pattern or color tone by distorted dissemination of powder because of difficulty of uniform dispersion of pulverulent body. On the other hand, though the key-top which is obtained by preparing the metallic film of aluminum or chrome on the surface of a formed body by the vacuum evaporation method or the sputtering method presents a metallic luster, it is not of transparent quality with a rainbow-colored brilliance.
Also, with regards to resin key-tops put into push button switches of recently used mobile phones, mobile terminals, various kinds of home electric appliances, card remote controls and various kinds keyboards, and so on, the demand for the key-tops having a fine and high-grade aspect is becoming stronger.